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Star Formation in NGC 5194 (M51a): The Panchromatic View fromGALEXtoSpitzer

Authors :: Karl D. Gordon
M. Sosey
J. D. T. Smith
George Helou
Max Mutchler
D. J. Hollenbach
S. Yi
A. Boselli
M. Polletta
Robert C. Kennicutt
M. J. Rieke
George J. Bendo
Fabian Walter
Eric J. Murphy
C. W. Engelbracht
D. C. Martin
L. J. Kewley
Luciana Bianchi
D. J. Lindler
Bruce T. Draine
Claus Leitherer
D. A. Thilker
Martin Meyer
B. F. Madore
H. Roussel
Daniel A. Dale
B. A. White
Michele D. Thornley
Nick Scoville
Kartik Sheth
D. Calzetti
L. Armus
Michael W. Regan
Samuel Boissier
George Rieke
Laboratoire d'Astrophysique de Marseille (LAM)
Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)
Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES)
Source :: The Astrophysical Journal, The Astrophysical Journal, 2005, 633, pp.871. ⟨10.1086/466518⟩, The Astrophysical Journal, American Astronomical Society, 2005, 633, pp.871. ⟨10.1086/466518⟩
Publication Year :: 2005
Publisher :: American Astronomical Society, 2005.
Abstract: (Abridged) Far ultraviolet to far infrared images of the nearby galaxy NGC5194, from Spitzer, GALEX, Hubble Space Telescope and ground--based data, are used to investigate local and global star formation, and the impact of dust extinction in HII-emitting knots. In the IR/UV-UV color plane, the NGC5194 HII knots show the same trend observed for normal star-forming galaxies, having a much larger dispersion than starburst galaxies. We identify the dispersion as due to the UV emission predominantly tracing the evolved, non-ionizing stellar population, up to ages 50-100 Myr. While in starbursts the UV light traces the current SFR, in NGC5194 it traces a combination of current and recent-past SFR. Unlike the UV emission, the monochromatic 24 micron luminosity is an accurate local SFR tracer for the HII knots in NGC5194; this suggests that the 24 micron emission carriers are mainly heated by the young, ionizing stars. However, preliminary results show that the ratio of the 24 micron emission to the SFR varies by a factor of a few from galaxy to galaxy. While also correlated with star formation, the 8 micron emission is not directly proportional to the number of ionizing photons. This confirms earlier suggestions that the carriers of the 8 micron emission are heated by more than one mechanism.<br />66 pages, 20 figures (Figures 1-4 are in JPEG format, figures 5-20 are embedded postscript files). Accepted for publication on the Astrophysical Journal